3 Reasons Your Pool Chlorine Isn’t Working

Phosphates are feeding the algae Leaves, lawn fertilizer, and even tap water introduce phosphates into your pool. Algae thrive on them, and your chlorine gets used up reacting to the phosphates instead of sanitizing the water.

High stabilizer (CYA) locks up chlorine CYA protects chlorine from the sun, but too much of it prevents chlorine from working at all. If your CYA is over 50–60 ppm, your chlorine is essentially neutralized.

High pH cuts chlorine’s effectiveness Chlorine works best when pH is between 7.2 and 7.6. Above that, its sanitizing power drops sharply, even if your test shows normal chlorine levels.